The Bengals enter Sunday’s game against the Patriots with an offense that has failed to gain 300 yards in either of its last two games, and a quarterback who is starting to lose the faith of his fan base.

But the 4-0 Patriots would be unwise to take the 2-2 Bengals lightly. The Bengals have a stout defense that is 10th in points allowed (20.2 per game), created seven turnovers in their first three games, and have an “outstanding” defensive line, Bill Belichick said. And they have one of the NFL’s best receivers in A.J. Green, two athletic tight ends in Jermaine Gresham and Tyler Eifert, and a good 1-2 running back combo of rookie Giovani Bernard and former Patriot BenJarvus Green-Ellis.

If not for a late collapse against the Bears in Week 1 and some poor bounces against the Browns in Week 4, the Bengals easily could be 4-0, with wins over the Steelers and Packers.

“There have been times we’ve played brilliantly, and then we’ve hurt ourselves,” coach Marvin Lewis said Monday. “We have to eliminate the self-inflicted wounds that we get — whether it be a free guy in a protection, which causes a turnover again, or a tipped ball that causes an interception, or a missed assignment which keeps us from converting a third down.”

The Bengals scored just 6 points in Sunday’s loss to the Browns, and third-year quarterback Andy Dalton is taking the brunt of the blame. He completed just 23 of 42 passes for 206 yards and an interception, although for the season he is completing 63.5 percent of passes with five touchdowns and four interceptions.

Green was noticeably frustrated Sunday after catching seven passes for 51 yards. He got off to a fast start this season, with nine catches for 162 yards and two touchdowns in Week 1, but hasn’t gone over 51 receiving yards in his last three games, with one touchdown.

“I think we were all a little frustrated [Sunday] when we don’t win,” Lewis said.

Patriots linebackers Jerod Mayo and Dont’a Hightower, who were beaten badly by Tony Gonzalez Sunday, will have another tough matchup with Gresham and Eifert, who have combined for 30 catches for 340 yards this year.

But the Patriots’ biggest issue may be slowing down Bernard and Green-Ellis with Vince Wilfork out. The duo had just 16 carries for 50 yards against the Browns, while Dalton had 44 dropbacks, and the Bengals seem intent on fixing that.

Bernard, a second-round pick out of North Carolina, has 147 rushing yards and two touchdowns on a 4.6 average this year, plus 12 catches for 122 yards. Green-Ellis, the short-yardage back, has 142 rushing yards and two touchdowns but is averaging just 2.7 yards per carry.

“We obviously have to be more effective running the football, continue to commit to running the football, and not get spooked away from it too often,” Lewis said.

The Patriots’ offense was able to push around the Falcons for 448 yards Sunday, but will have a much tougher time against the Bengals, whose defense revolves around Geno Atkins, a two-time Pro Bowler and perhaps the best defensive tackle in the NFL. Defensive ends Carlos Dunlap and Michael Johnson have combined for 4½ sacks, and the Bengals have an experienced linebacker corps led by ex-Steeler James Harrison, plus Rey Maualuga and rising young star Vontaze Burfict, who suffered a minor neck injury last Sunday.

The Bengals have an opportunistic secondary with four interceptions this year, but cornerbacks Leon Hall and Dre Kirkpatrick are questionable with hamstring injuries, as is safety Reggie Nelson.

The Bengals have held Jay Cutler, Ben Roethlisberger, Aaron Rodgers, and Brian Hoyer under 250 passing yards each and allowed only the Packers to rush for more than 90 yards.